A need continues to grow for more complex semiconductor (SC) devices and integrated circuits (IC) incorporating integrated passive devices. Non-limiting examples of such passive devices are inductors, capacitors, resistors, interconnections, transmission lines, baluns, couplers, filters, various other high frequency components, and so forth. For manufacturing and performance efficiency it is advantageous to form the passive devices on the same substrate as the transistors and/or other active devices used to implement the desired electronic function. Hence, the description “integrated passive devices”, abbreviated as “IPD”.
The performance and cost of many devices, especially radio frequency (RF) power devices and integrated circuits (ICs), are particularly sensitive to losses and layout rules associated with such integrated passive devices and to their occupied area. Electro-magnetic (E-M) coupling of IPDs to the semiconductor substrates on which they are formed can give rise to eddy current losses in the substrate that can degrade overall device and IC performance. These problems become more severe with high periphery and higher frequency devices. When the IPDs incorporate resonant elements (e.g., inductors, capacitors, transmission lines, filters, etc.) the E-M coupling between such IPDs and the underlying semiconductor substrate can degrade the “Q” of the IPDs and result in significant overall circuit losses. (The quality factor Q is a measure of the energy stored divided by the energy dissipated per cycle by a resonant element). Such losses can occur with any type of integrated passive device, not just those listed above. Another concern is the area occupied by the IPDs and the connections leading thereto. If forming the IPDs interacts adversely with the associated active devices, this can require larger minimum separation between the active devices and the IPDs. When that occurs, the performance can be further degraded because of the increase in coupling losses associated with longer interconnections. Further, the overall manufacturing cost also increases in proportion to the increase in total occupied area. Thus, any adverse interactions between the IPDs and associated active devices that leads to increased element spacing, greater coupling losses and larger chip area is undesirable.
Accordingly, a need continues to exist for improved device structures and fabrication methods, that reduce the parasitic E-M coupling and losses associated with integrated passive devices (IPDs) formed on the same substrate as their associated transistors and other active devices. It is also important that inter-element spacing associated with placing the IPDs on the same substrate as the active devices be minimized so as to avoid area bloat and/or further coupling losses associated with increased separation between the active devices and the IPDs.